As described in Patent Document 1, internal combustion engines having a port injector for injecting fuel into an intake port and a direct injector for injecting fuel into a cylinder have been mounted in vehicles. These engines perform dual-injection, in which fuel injection by the amount corresponding to an injection amount command value, which is determined based on an engine operating state, is carried out through the port injector and the direct injector in a divided manner at a dual-injection rate, which is obtained in accordance with the engine operating state.
In the dual-injection, fuel is injected from the port injector and the direct injector in the manner described below, for example. Specifically, the injection amount command value is divided into a port injection command value and a direct injection command value in accordance with the dual-injection rate, which is determined in accordance with the engine operating state. The port injector injects fuel by an amount corresponding to the port injection command value and the direct injector injects fuel by an amount corresponding to the direct injection command value.
The amount of fuel injected by each of the injectors, which are the port injector and the direct injector, is determined based on the pressure of the fuel supplied to each injector and the valve opening time (the fuel injection time) of the injector. Accordingly, for the port injector in the dual-injection, the fuel injection time of the port injector is controlled such that the amount of fuel corresponding to the port injection command value is injected under the pressure of the fuel currently supplied to the port injector. Similarly, for the direct injector in the dual-injection, the fuel injection time of the direct injector is controlled such that the amount of fuel corresponding to the direct injection command value is injected under the pressure of the fuel currently supplied to the direct injector.